While touch panels or touch screens have been extant for more than a decade, they are suddenly gaining popularity for use with interactive display devices, such as computer trminals and electronic test and measurement equipment. Touch panels have been implemented in a variety of different methods, including touch-sensitive capacitive areas, pressure sensitive screens, and "break-the-beam" light matrices for sensing X-Y screen coordinates. Most popular of these because it has the least operational problems and is easiest to implement is the "break-the-beam" type, which comprises an array of paired light emitting diodes (LEDs) and phototransistors on four sides of a display screen to form an X-Y light-beam grid that is sequentially scanned in repetitive cycles. When a light beam is interrupted by an obstacle, such as a stylus or a finger, the X-Y coordinate point is electronically decoded and sent to a computer.
A problem associated with light-beam matrix touch panels is the large number of components required, particularly if high resolution is desired. It would be desirable to retain high resolution while reducing the part count, thereby lowering power consumption, reducing scan cycle times, and reducing manufacturing costs.